Arbitrary File Write via Archive Extraction (Zip Slip) Affecting github.com/bblfsh/bblfshd/runtime package, versions *


0.0
medium

Snyk CVSS

    Exploit Maturity Proof of concept
    Attack Complexity High
    User Interaction Required
    Scope Changed
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NVD
9.1 critical

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  • Snyk ID SNYK-GOLANG-GITHUBCOMBBLFSHBBLFSHDRUNTIME-1566478
  • published 17 Aug 2021
  • disclosed 17 Aug 2021
  • credit Chris Smowton

How to fix?

A fix was pushed into the master branch but not yet published.

Overview

github.com/bblfsh/bblfshd/runtime is a provides the runtime environment to execute the bblfsh drivers.

Affected versions of this package are vulnerable to Arbitrary File Write via Archive Extraction (Zip Slip). The unsafe handling of symbolic links in an unpacking routine may enable attackers to read and/or write to arbitrary locations outside the designated target folder.

Details

It is exploited using a specially crafted zip archive, that holds path traversal filenames. When exploited, a filename in a malicious archive is concatenated to the target extraction directory, which results in the final path ending up outside of the target folder. For instance, a zip may hold a file with a "../../file.exe" location and thus break out of the target folder. If an executable or a configuration file is overwritten with a file containing malicious code, the problem can turn into an arbitrary code execution issue quite easily.

The following is an example of a zip archive with one benign file and one malicious file. Extracting the malicous file will result in traversing out of the target folder, ending up in /root/.ssh/ overwriting the authorized_keys file:


+2018-04-15 22:04:29 ..... 19 19 good.txt

+2018-04-15 22:04:42 ..... 20 20 ../../../../../../root/.ssh/authorized_keys